Beam and a method of forming same

ABSTRACT

A beam ( 10 ) including a metal outer skin ( 12 ) formed into a closed shape and an inner core ( 16 ) formed from expanded foam material. The outer surfaces of the inner core ( 16 ) are bonded to the inner surfaces of the outer skin ( 12 ). A method of forming a beam ( 10 ) is also disclosed.

TECHNICAL FIELD

[0001] The present invention relates to a beam and a method of forming same.

[0002] The invention has been primarily developed in relation to a light weight beam suitable for home extensions and will be described hereinafter with reference to this application. However, it will be appreciated that the beam is not limited to this particular use and is also suitable for new building construction, renovations and scaffolding.

BACKGROUND OF THE INVENTION

[0003] A known light weight beam is marketed by BHP Company as FIRMLOK (Trade Mark). This beam is produced by crimping together two generally U-shaped, roll-formed, steel channels to form a closed rectangular beam.

[0004] The main disadvantage of this beam is it is produced in two stages, namely roll-forming the two channels and then assembling and crimping them together. This is a complicated and relatively expensive process. Another disadvantage of this beam is that fasteners inserted between the opposing sides of the beam can cause the sides to bow together, which is unsightly.

OBJECT OF THE INVENTION

[0005] It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above noted prior art disadvantages.

SUMMARY OF THE INVENTION

[0006] Accordingly, in a first aspect, the present invention provides a beam including:

[0007] a metal outer skin formed into a closed shape; and

[0008] an inner core formed from expanded foam material,

[0009] wherein the outer surfaces of the inner core are bonded to the inner surfaces of the outer skin.

[0010] In one form, the outer skin closed shape is formed by folding, with opposed longitudinal edges of the outer skin most preferably being joined by a folded seam. In another form, the outer skin closed shape is formed by extruding.

[0011] In one embodiment the outer skin has a rectangular cross-section. In another embodiment, the outer skin has a round cross-section.

[0012] In a second aspect, the present invention provides a method of forming a beam, the method including:

[0013] (1) forming a metal outer skin of a closed shape; and

[0014] (2) introducing an expandable foam material into the interior of the outer skin to form an inner core,

[0015] whereby the outer surfaces of the inner core expand and bond to the inner surfaces of the outer skin.

[0016] Step (1) is preferably performed by roll forming.

[0017] In one embodiment, step (2) is performed by introducing the expandable foam material into the interior of the outer skin after it is fully closed. Step (2) preferably includes: tilting the closed outer skin until its longitudinal axis is at an angle acute to vertical or is vertical; plugging its lower end; and injecting the foam material into its interior, most preferably at spaced apart locations.

[0018] In another embodiment, step (2) is performed by introducing the expandable foam material into the interior of the outer skin prior to it being fully closed. Step (2) preferably includes continuously injecting the foam material into the interior of the outer skin in advance of the closing fold.

[0019] Alternatively, step (1) is performed by extruding.

[0020] In a further embodiment, step (2) is performed by introducing the expandable foam material into the interior of the outer skin after it is formed. Step (2) preferably includes tilting the closed outer skin until its longitudinal axis is at an angle acute to vertical or is vertical; plugging its lower end; and progressively injecting the foam material into the interior beginning substantially adjacent the lower end and ending substantially adjacent its upper end.

[0021] In a third aspect, the present invention provides a beam including:

[0022] a metal outer skin formed into a closed shape; and

[0023] an inner core formed from expanded foam material.

[0024] In a fourth aspect, the present invention provides a method of forming a beam, the method including:

[0025] (1) forming a metal outer skin of a closed shape, and

[0026] (2) introducing an expandable foam material into the interior of the outer skin to form an inner core that expands and bonds to the inner surfaces of the outer skin.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0028]FIG. 1a is a cross sectional end view of first embodiment of a beam according to the invention;

[0029]FIG. 1b is an enlarged detailed view of a closing seam used in the beam shown in FIG. 1a;

[0030]FIG. 2 is a cross sectional side view of the beam shown in FIG. 1a during manufacture;

[0031]FIG. 3a is a cross sectional side view of a second embodiment of a beam according to the invention during manufacture; and

[0032]FIG. 3b is a cross sectional end view of the completed beam shown in FIG. 3a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Referring firstly to FIGS. 1a and 1 b, there is shown a beam 10 according to a first embodiment of the present invention. The beam 10 is formed from a 0.55 mm thick sheet metal outer skin 12 which is folded into a rectangular cross-sectional closed shape having dimensions of 150 mm by 55 mm. The skin 12 is preferably formed from COLORBOND (Trade Mark) material, as marketed by BHP Company, which is available in numerous colours.

[0034] The beam 10 has a longitudinal seam 14 in one of its shorter sides. Both the forming into the rectangular shape and the closing seam 14 are produced using a roll-former configured in a manner similar to that used in making rainwater down pipes, except the seam 14 is placed in one of the shorter sides, not one of the longer. Such roll-forming is well understood by persons skilled in the art.

[0035] The beam 10 also includes an inner core 16 formed from expanded foam material. The foam material is preferably polyisocyanurate (PIR) foam which is similar to a standard polyurethane foam but which exhibits enhanced fire performance. The foam material is injected into the interior of the beam 10 in liquid form and expands until its outer surfaces contact, and bond with, the inner surfaces of the outer skin 12.

[0036] The adhesive bond formed between the outer surfaces of the inner core 16 and the inner surfaces of the outer skin 12 results in the beam 10 exhibiting surprisingly high levels of strength relative to its weight.

[0037] The beam 10 was tested against an equivalent size FIRMLOK F150-15 beam. In the test, a 4,800 mm section of each beam was supported by its ends. An increasing load was then applied to the central 200 mm of each beam. The beam 10 exhibited slightly higher levels of deflection than the FIRMLOK beam. For example, under a load of 150 kg, the beam 10 flexed approximately 19 mm as compared to the 13 mm flexure of the FIRMLOK beam. However, whilst the beam 10 deflected slightly more it is important to note that the beam 10 is approximately 50% lighter than the correspondingly sized FIRMLOK beam. The beam 10 thus represents a substantial strength to weight improvement over an equivalent FIRMLOK beam. Further, the FIRMLOK beam exhibited a (lateral buckling) failure at 170 kg whilst the beam 10 did not fail until a 230 kg load (due to local crimping of the top flange).

[0038] An embodiment of a method of producing the beam 10 will now be described with reference to FIG. 2. Firstly, the outer skin 12 of the beam is formed by roll-forming. An end 18 of the beam is then sealed with a removable plug 20. Two holes are then drilled approximately 2 meters and 4 meters from the plug 20 at the points indicated by arrows 22 and 24.

[0039] The beam 10 is then tilted until its longitudinal axis is at an angle acute to vertical. Liquid expandable foam material is then injected through the hole 22 until it has filled and expanded past the bole 22. Additional liquid expandable foam material is then injected through the hole 24 until it has filled and expanded through the other end 26 of the beam 10.

[0040] When the foam material has expanded and set the plug 20 is removed and any excess foam material is trimmed from the beam end 26.

[0041] In addition to the strength to weight advantages described above, the beam 10 is also simpler and cheaper to produce than the FIRMLOK beams. Further, the foam inner core 16 resists bowing of the longer sides of the beam 10 when fasteners are inserted therethrough.

[0042] Referring to FIGS. 3a and 3 b there is shown a beam 30 according to a second embodiment of the present invention. The beam 30 is formed from an extruded aluminium outer skin 32, having a circular cross sectional closed shape. As with the first embodiment, the beam 30 also has an inner core 33 formed from expandable foam material.

[0043] The beam 30 is produced by initially sealing a lower end of the skin 32 with a removable plug 34. The skin is then oriented until its longitudinal axis is about vertical. A hose 36 is then lowered into the interior of the skin 32 until its end 38 is adjacent the plug 34. Liquid expandable foam material 40 is then injected through the hose 36 into the interior of the skin 32, in the direction indicated by arrows 42. As the foam material 40 expands to fill the skin 32, the hose 36 is progressively withdrawn from the skin 32, in the direction of arrow 44, until the entire interior of the skin 32 is filled. When the foam material 40 has expanded and set, the plug 34 is removed and the excess foam material is trimmed from the upper beam end.

[0044] In addition to the strength to weight advantages described above, the circular cross section beam 30 also exhibits enhanced flexibility, making it particularly suitable for structures subject to cyclonic conditions and/or for scaffolding structures.

[0045] Although the invention has been described with reference to preferred embodiments, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. For example, the beam can also be produced in other industry standard sizes such as 75 mm by 50 mm, 75 mm by 100 mm and 100 mm by 100 mm. Other types of expandable foam materials can also be used, The beam can also be produced by continuously injecting the foam material into the outer skin during the roll forming process, with the injecting nozzle positioned just in front of the closing seam. The outer skin of the beam can also be folded into various shapes other than rectangular and can also be extruded in various cross sections other than circular. 

I claim:
 1. A beam including: a metal outer skin formed into a closed shape; and an inner core formed from expanded foam material, wherein the outer surfaces of the inner core are bonded to the inner surfaces of the outer skin.
 2. A beam as claimed in claim 1, wherein the outer skin closed shape is formed by folding.
 3. A beam as claimed in claim 2, wherein opposed longitudinal edges of the outer skin are joined by a folded seam.
 4. A beam as claimed in claim 1, wherein the outer skin closed shape is formed by extruding.
 5. A beam as claimed in claim 1, wherein the outer skin has a rectangular cross-section.
 6. A beam as claimed in claim 1, wherein the outer skin has a round cross-section.
 7. A method of forming a beam, the method including: (1) forming a metal outer skin of a closed shape; and (2) introducing an expandable foam material into the interior of the outer skin to form an inner core, whereby the outer surfaces of the inner core expand and bond to the inner surfaces of the outer skin.
 8. The method as claimed in claim 7, wherein Step (1) is performed by roll forming.
 9. The method as claimed in claim 7, wherein Step (2) is performed by introducing the expandable foam material into the interior of the outer skin after it is fully closed.
 10. The method as claimed in claim 9, wherein Step (2) includes: tilting the closed outer skin until its longitudinal axis is at an acute angle to vertical or is vertical; plugging its lower end; and injecting the foam material into its interior
 11. The method as claimed in claim 10, wherein the foam material is injected at spaced apart locations.
 12. The method as claimed in claim 7, wherein Step (2) is performed by introducing the expandable foam material into the interior of the outer skin prior to it being fully closed.
 13. The method as claimed in claim 12, wherein Step (2) includes continuously injecting the foam material into the interior of the outer skin in advance of the closing fold.
 14. The method as claimed in claim 7, wherein Step (1) is performed by extruding.
 15. The method as claimed in claim 7, wherein Step (2) is performed by introducing the expandable foam material into the interior of the outer skin after it is formed.
 16. The method as claimed in claim 15, wherein Step (2) includes tilting the closed outer skin until its longitudinal axis is at an acute angle to vertical or is vertical; plugging its lower end; and progressively injecting the foam material into the interior beginning substantially adjacent the lower end and ending substantially adjacent its upper end.
 17. A beam including: a metal outer skin formed into a closed shape; and an inner core formed from expanded foam material.
 18. A method of forming a beam, the method including: (1) forming a metal outer skin of a closed shape; and (2) introducing an expandable foam material into the interior of the outer skin to form an inner core that expands and bonds to the inner surfaces of the outer skin. 